This invention generally relates to the art of electrical switches and, particularly, to laminated electrical switches of the push-button type.
Push-button electrical switches have been designed in a wide variety of configurations for a wide variety of applications. Such switches range from substantial three-dimensional structures having box-like housings to very thin or laminated switches, sometimes called xe2x80x9cmembranexe2x80x9d switches. Thin laminated switches often are used in conjunction with printed circuit boards. This invention is directed to improvements in such laminated switches.
An object, therefore, of the invention is to provide a new and improved electrical switch of the character described.
In the exemplary embodiment of the invention, the electrical switch includes an insulative substrate having a lower stamped metal circuit sheet supported thereon. The lower sheet includes a plurality of switch contacts and a plurality of leads for connecting the switch contacts to appropriate conductors. An upper stamped metal sheet is disposed over the insulative substrate and includes a plurality of embossed metal domes in registry with respective ones of the switch contacts. Depression of a selected one of the embossed metal domes engages the dome with a respective one of the switch contacts to close a circuit therethrough.
As disclosed herein, the lower stamped metal circuit sheet is insert molded in the insulative substrate and includes a common contact in engagement with the upper stamped metal sheet. The common contact is in the form of a peripheral contact outside the plurality of switch contacts. The upper stamped metal sheet includes a peripheral frame outside the plurality of embossed metal domes. The peripheral frame is in engagement with the peripheral contact. The plurality of embossed metal domes are electrically coupled to the peripheral frame.
A feature of the invention includes the insulative substrate having a plurality of integral pegs extending through apertures in the peripheral contact of the lower stamped metal circuit sheet and through apertures in the peripheral frame of the upper stamped metal sheet. The pegs are deformed, as by staking, to hold the upper stamped metal sheet and the insulative substrate together, with the peripheral contact in engagement with the peripheral frame.
In an alternative embodiment of the invention, an insulated circuit sheet is disposed between the upper stamped metal sheet and the insulative substrate. The insulated circuit sheet includes conductive pads in registry between the embossed metal domes and the switch contacts. The insulated circuit sheet is configured to hermetically seal the insulative substrate and lower stamped metal circuit sheet.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.